• 한국정밀공학회지
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• 제19권8호
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• pp.147-154
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• 2002

In this paper, a path navigation algorithm through use of a sensor platform is proposed. The sensor platform is composed of two electric motors which make panning and tilting motions. An algorithm for computing a real path and an obstacle length is developed by using a scanning method that controls rotation of the sensors on the platform. An Autonomous Robot Vehicle(ARV) can perceive the given path by adapting this algorithm. A sensor scanning method is applied to the sensor platform for using small numbers of sensor. The path navigation algorithm is composed of two parts. One is to perceive a path pattern, the other is used to avoid an obstacle. An optimal controller is designed for tracking the reference path which is generated by perceiving the path pattern. The ARV is operated using the optimal controller and the path navigation algorithm. Based on the results of actual experiments, this algorithm for an ARV proved sufficient for path navigation by small number of sensors and for a low cost controller by using the sensor platform with a scanning method.

• 한국안전학회지
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• 제13권4호
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• pp.162-171
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• 1998

This paper presents the harmonics obstacle analysis and countermeasure of electrical consumption a place. Harmonics that can be cosidered as a environmental pollution of the power systems become the cause of the accidents and damages. The responsibility of eliminating the harmonics firstly lies on the generating side. But the original characteristics of the system sush as the harmonic transfer characteristics and the impedance of the system affect each other in the process of the generation and transmission of the harmonic. Therefore it is very difficult to specify clearly the harmonic controlling responsibility, because electric machinery generating harmonics are various in the industrial fields. The output of a inverter has a high harmonic content. There are several ways of minimizing the output harmonic content. One way is to use pulse width modulation techniques within inverter. An alternative method is to combine a number of square-wave inverters. In this research, we measure the harmonic of the countermeasure of electrical consumption a place. The paper present the problem of new harmonic elimination method of PWM inverter fed induction motor system using W-FT series. In the future, the proposed PWM pattern by W-FT series is effective not only to the induction motor but also to the electromagnetic machine such as voltage reglator, UPS.

• 한국정밀공학회지
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• 제32권5호
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• pp.471-481
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• 2015

This paper presents the robot vision control schemes using Extended Kalman Filter (EKF) method for the slender bar placement in the appearance of obstacles during robot movement. The vision system model used for this study involves the six camera parameters($C_1{\sim}C_6$). In order to develop the robot vision control scheme, first, the six parameters are estimated. Then, based on the estimated parameters, the robot's joint angles are estimated for the slender bar placement. Especially, robot trajectory caused by obstacles is divided into three obstacle regions, which are beginning region, middle region and near target region. Finally, the effects of number of obstacles using the proposed robot's vision control schemes are investigated in each obstacle region by performing experiments of the slender bar placement.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.399-399
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• 2000

In this paper, path generation using the sensor platform is proposed. The sensor platform is composed two electric motors which make panning and tilting motions. An algorithm fur a real path form and an obstacle length is realized using a scanning algorithm to rotating the sensors on the sensor platform. An ARV (Autonomous Robot Vehicle) is able to recognize the given path by adapting this algorithm. In order for the ARV to navigate the path flexibly, a kinematic model needed to be constructed. The kinematic model of the ARV was reformed around its body center through a relative velocity relationship to controllability, which derives from the nonholonomic characteristics. The optimal controller that is based on tile kinematic model is operated purposefully to track a reference vehicle's path. The path generation algorithm is composed of two parks. On e part is the generating path pattern, and the other is used to avoid an obstacle. The optimal controller is used for tracking the reference path which is generated by recognizing the path pattern. Results of simulation show that this algorithm for an ARV is sufficient for path generation by small number of sensors and for low cost controller.

• 대한기계학회논문집B
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• 제32권10호
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• pp.791-799
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• 2008

We investigate the flow characteristics around a series of rectangular bodies ($40^d{\times}80^w{\times}80^h$, $80^d{\times}80^w{\times}80^h$ and $160^d{\times}80^w{\times}80^h$) placed in a deep turbulent boundary layer. The study is aiming to understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge, when the flow is normal, which is responsible for producing extreme suction pressures on the roof. The experiment includes wind tunnel work by using HWA (Hot-Wire anemometry) and pressure transducers. The experiments are carried out at three different Reynolds numbers, based on the velocity U at the body height h, of $2.4{\times}10^4$, $4.6{\times}10^4$ and $6.7{\times}10^4$, and large enough that the mean flow is effectively Reynolds number independent. The results include the measurements of the growth of the turbulent boundary layer in the wind tunnel and the surface pressure around the bodies.

• 대한임베디드공학회논문지
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• 제12권1호
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• pp.43-62
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• 2017

Mobile pulse scanning Light Detection And Ranging (LIDAR) are essential components of intelligent vehicles capable of autonomous travel. Obstacle detection functions of autonomous vehicles require very low failure rates. With the increasing number of autonomous vehicles equipped with scanning LIDARs to detect and avoid obstacles and navigate safely through the environment, the probability of mutual interference becomes an important issue. The reception of foreign laser pulses can lead to problems such as ghost targets or a reduced signal-to-noise ratio. This paper will show the probability that any two scanning LIDARs will interfere mutually by considering spatial and temporal overlaps. We have conducted four experiments to investigate the occurrence of the mutual interference between scanning LIDARs. These four experimental results introduced the effects of mutual interference and indicated that the interference has spatial and temporal locality. It is hard to ignore consecutive mutual interference on the same line or the same angle because it is possible the real object not noise or error. It may make serious faults because the obstacle detection functions of autonomous vehicle rely on heavily the scanning LIDAR.

• 사물인터넷융복합논문지
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• 제7권4호
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• pp.29-34
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• 2021

실 환경에서 로봇에 강화학습을 적용하기 위해서는 수많은 반복 학습이 필요하므로 가상 환경에서의 시뮬레이션을 사용할 수밖에 없다. 또한 실제 사용하는 로봇이 저사양의 하드웨어를 가지고 있는 경우 계산량이 많은 학습 알고리즘을 적용하는 것은 어려운 일이다. 본 연구에서는 저사양의 하드웨어를 가지고 있는 모바일 로봇의 장애물 충돌 회피 문제에 강화학습을 적용하기 위하여 가상의 시뮬레이션 환경으로서 Unity에서 제공하는 강화학습 프레임인 ML-Agent를 활용하였다. 강화학습 알고리즘으로서 ML-Agent에서 제공하는 DQN을 사용하였으며, 이를 활용하여 학습한 결과를 실제 로봇에 적용해 본 결과 1분간 충돌 횟수가 2회 이하로 발생하는 결과를 얻을 수 있었다.

• 대한기계학회논문집B
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• 제32권12호
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• pp.924-930
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• 2008

Immersed boundary method (IBM) is the most effective method to overcome the disadvantage of LBM (Lattice Boltzmann Method) related to the limitation of the grid shape. IBM also make LBM possible to simulate flow over complex shape of obstacle without any treatment on the curved boundary. In the research, IBLBM was used to perform LBM simulation of a flow over a moving circular cylinder to determine the flow feature and aerodynamics characteristic of the cylinder. To ascertain the applicability of IBLBM on the moving obstacle near the wall, it was first simulated for the case of the flow over a fixed circular cylinder in a channel and the results were compared against the solution of moving cylinder in the channel using IBLBM. The simulations were performed in a moderate range of Reynolds number at each moving cylinder to identify the flow feature and aerodynamic characteristics of circular cylinder in a channel. The drag and lift coefficients of the cylinder were calculated from the simulation results. We have numerically confirmed that the critical Reynolds number for vortex shedding is Re=50 and the result is the same as the case of fixed cylinder. As the cylinder approaching to a wall (${\gamma}<2.5$), the 2nd vortex is developed by interacting with the wall boundary-layer vorticity. When the cylinder is very closed to the wall, ${\gamma}<0.6$, the cylinder acts like blockage to block the flow between the cylinder and wall so that the vortex developed on the upper cylinder elongated and time averaged lifting and drag coefficients abruptly increase.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1128-1131
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• 1996

The collision-free path planning presented here uses linear parametric curve with one intermediate connection point between start and target points. The algorithm, in which connection point is organized in elliptic chord.(.theta., .delta.), maps objects in Euclidean Space into images in CPS through intersection check between path and obstacles a process defined as GM. Elliptic locus has special property that the total distance between focus points through a point on ellipse is the same regardless of .theta.. Hence by locating the start and target points to focus points of ellipse, and organizing connection point in elliptic coordinate, the .delta.-axis of CPS represents length of path. The GM of EWS requires calculation of interference in circumferential direction only. The procedures for GM is developed which include categorization of obstacles to reduce calculation amount. Simulations of GM of EWS, on a PC with Pentium/90MHz, is carried out to measure performance of algorithm and the results are reported on a table. The simulations are done for number of cases with different number of obstacles and location of start/target points.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권5호
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• pp.309-314
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• 2004

In the established virtual-reality system, although it is possible to transact a faculty of sensation and graphic in a single PC, virtual object forcibly treated with rigid body for the reason of the huge amount of calculation, and the number of polygon is restricted. Furthermore, there is some difficulty in the financial aspect and a program field, because the existing virtual-reality system needs at least two workstations or super computers. In this study, the new force-reflecting algorithm called as "Proxy" and a finite element method of Hyperion are applied to this system in order to transact in real-time. Consequently, though the number of polygon, which brings about an obstacle is increased in the real-time graphic transaction, this system makes it possible to transact in the real-time, not being influenced by the size of the virtual object.